Defective/monocyte-macrophage (MO) antigen presenting (APC) and aberrantly increased monokine production are major contributors to post- trauma immune depression as well as cytokine shock and end-organ failure. We hypothesize that post-trauma immunosuppression and production of excessive monokines like TNFalpha, PGE2 and TGFBeta have a cause and effect relationship. Monocyte-macrophage activation/differentiation in the absence of T lymphokines and in the presence of excessive monokines results in development of unique monocyte-macrophage subsets with aberrant response and T cell induction capacities. These unique monocyte-macrophage subsets have altered receptor/ligand expression which prevents them from appropriately activating T lymphocytes, thereby perpetuating immunosuppression. these unique receptor/ligand combinations also allow monocyte/macrophage to become overstimulated by trauma generated mediators, desensitized to normal monokine downregulation mechanisms, overproductive of immunosuppressive monokines and underproductive of T cell stimulatory-monokines, thereby insuring a continued cycle of depressed T cell activity and increased pathologic monokine production. We propose to first, characterize at the protein level using ELISA and bioassays as well as at the mRNA levels using the quantitative MIMIC polymerase chain reaction (PCR), altered monokine production which could contribute to cytokine shock and/or immune depression examining increased or depressed production of regulatory monokines such as IL-10, PGE2 and TGFBeta as well as pro-inflammatory mediators such as TNFalpha, IL-6, IL-8 and MIP-1. Production of T lymphocytes as IFNgamma, IL-4, IL-13 and IL-10 which control monocyte- macrophage function will be assessed. Altered monocyte-macrophage APC function in the tetanus toxoid system will be defined for the degree of T cell activation and production levels of the T stimulatory monokine IL- 12. Responsiveness of monocyte-macrophage to monokine downregulation by IL-4, IL-10 and IL-13 will be assessed. Second, we propose to delineate the post-trauma appearance of monocyte-macrophage expressing altered receptor/ligand combinations which can alter their response to the post- trauma microenvironment such as increased FcgammaRI, increased urokinase receptor, altered TNFR expression, decreased PGE2 receptors, decreased T cell costimulators such as HLA DQ CD45RA, CD4 or B7, or increased expression of LPS receptors (CD14) and C3b receptors CD11b using three color flow cytometry. Third, we will correlate the post-trauma alteration in these monocyte-macrophage subsets to patient monocyte- macrophage dysfunctions. The identified subset will be characterized for their differential responsiveness to trauma generated mediators known to be monocyte-macrophage augmentors. Finally, an FcgammaRI activated normal monocyte-macrophage will be used as a model for post-trauma alteration in transcriptional or translational regulation of monocyte- macrophage TNFalpha mRNA induction in response to mediators in the trauma microenvironment examining transcription rates (nuclear run-on), transcriptional/translational inhibitors (cycloheximide) and mRNA stability changes (actinomycin D). These experiments identify monocyte- macrophage phenotypes indicative of dysfunction development which could be monitored post-injury as well as dissect post-trauma aberrant activation and regulation pathways.